Scratch is a free educational programming language that was developed by the Lifelong Kindergarten Group at the Massachusetts Institute of Technology (MIT). The current version, 2.0, can be downloaded here (the previous version, 1.4, can be downloaded here) or accessed with the online editor here.
Scratch is designed to be fun, educational, and easy to learn. It has the tools for creating interactive stories, games, art, simulations, and more. Scratch even has its own paint editor and sound editor built-in.
Users program in Scratch by dragging blocks from the block palette and attaching them to other blocks like a jigsaw puzzle. Structures of multiple blocks are called scripts. This method of programming (building code with blocks) is referred to as "drag-and-drop programming".
Scratch is used in schools around the world as a means of introducing basic computer programming to children. It is also used outside of schools, usually introduced by friends or parents. Children and even adults gain an understanding of the fundamentals of programming with Scratch, and often move on to other programming languages. During their use of Scratch, people can create, remix, and collaborate with others on Scratch projects.
In designing the language, the creators' main priority was to make the language and development environment intuitive and easily learned by children who had no previous programming experience. There is a strong contrast between the powerful multimedia functions and multi-threaded programming style and the rather limited scope of the Scratch programming language.user interface for the Scratch development environment divides the screen into several panes: on the in the middle is the blocks palette, on the right the scripts area, and on the left the stage and sprite list. The blocks palette has code fragments (called "blocks") that can be dragged onto the scripts area to make programs. To keep the palette from displaying a great quantity of blocks and for ease if use, it is organized into 10 groups of blocks: motion, looks, sound, pen, control, events, sensing, operators, variables, and more blocks.
Origin of the Word
"Scratch" was used as the title for The Lifelong Kindergarten Group's programming language, as it is to do with "scratching" referring to music.
|“||Scratching is a DJ or turntablist technique used to produce distinctive sounds by moving a vinyl record back and forth on a turntable while optionally manipulating the crossfader on a DJ mixer.||”|
Likewise, within Scratch, you take different bits of code (blocks), put them together, and have made something new.
|“||We take the name "Scratch," from the way that hip-hop disk jockeys scratch with music. They take pieces of music and then combine them together in unexpected and creative ways.||”|
– Mitchell Resnick, Lifelong Kindergarten Group at MIT
Variants of the Word
The word "Scratch" has spawned other phrases that have become popular amongst users of Scratch:
- Scratcher — A user of Scratch
- Scratching — A verb which means to use Scratch
- Scratched — A project that is an attempted replica of another game. e.g. "Pac-man Scratched"
- Scratch Time — The timezone that the forums are set in (EST/EDT)
- Scratch On! — A phrase coined by the Scratch Team, and used by them (although has been adapted by other Scratchers as well) to encourage users, meaning "carry on using Scratch"
Scratch's motto is Imagine • Program • Share. This follows the basic principle of creating a Scratch Project. First of all, you think of an idea (imagine), next, you program your idea in Scratch (program), then finally share it with the world (share). Since the release of Scratch 2.0, the motto has been less apparent throughout the website; the front page no longer has the motto but instead a description of what Scratch is.
- Main article: Scratch Versions
Scratch is currently on version 2.0, the online editor officially released on May 9, 2013 and the offline editor on August 26, 2013. It's predecessor is Scratch 1.4, which was released on July 2, 2009. The previous, older versions are Scratch 1.3, Scratch 1.2, Scratch 1.1, and Scratch 1.0. Each version had significant changes, especially the jump from 1.4 to 2.0. Not only did the program update with version 2.0, but the entire website evolved.
- Scratch is turing complete.
- It is primarily event-driven.
- Whether or not it is OOP is debated in the community.
- Scratch has variables and lists for data storage, and arrays can be replicated.
- Scratch is not atomic in repetition, though that can be simulated with Single Frame programming.
- Scratch 2.0 does support procedures, and recursion.
- Scratch has many simplified casting rules. Data isn't, however, first-class — you cannot have first-class lists, sprites, or procedures (lambda).
Scratch has limited hardware/OS access, and is supposed to be a very "safe" programming language. The following can be accessed by Scratch:
- Ambient volume
- Mouse position relative to the Scratch frame
- Key presses, only if Scratch is in focus
- In Scratch 2.0, your movements will be provided as sensor values, using a webcam for image input.
- The filesystem can be accessed while in development, but not while running.
Scratch Modifications offer more OS permissions.
- Main article: Scratch Jr
Scratch Jr is an even simpler programing language that will be used on mobile. It's for kids ages 5 to 7 years old. The development team is different from the Scratch Team, though a couple of members contribute to both programs.
- Getting Started with Scratch
- Scratch on Wikipedia — the description of Scratch on an external website
- Scratch Programming Language — analyzing Scratch as a programming language
- Scratch 2.0 — the current version of the Scratch website and program
- Programming Language — what they are and their uses to the world of computer science